The invention relates generally to power-driven conveyors and more particularly to motorized pulleys and conveyor-belt drive systems.
Wide belt conveyors use long drive shafts on which drive pulleys or sprockets driving a conveyor belt are mounted. The drive shaft is conventionally rotated by a gear motor at one end of the shaft. When the belt is lightly loaded, the shaft 20 is true—untwisted as in FIG. 14A. But a high belt load creates a torsional load 22 in the shaft 20 that acts in an angular direction opposing the drive torque 24 at the drive end 27 of the shaft, as shown in FIG. 14B. The torsional load causes the drive shaft 20 to twist about its axis and creates a maximum angular deflection b of the shaft 20 between the drive end 27 and the opposite end 26 of the shaft. Angular deflection of the shaft 20 changes the phases of sprocket teeth along the length of the shaft from the phase of the sprocket closest to the drive end 27. Shaft twist can cause improper engagement of the sprocket teeth with the conveyor belt.